The decal you uncovered is clearly not the same decal as the M42 you posted after. Look at the feathers on the chest of the eagle, especially the lowest one in between the legs. The swastika is also much thinner on the uncovered decal. It's a fake decal in my opinion also.

ok did some research on the kriegsmarine decal , there were several different makers for this decal I believe mine matches the fourth image my helmet are the first three pics , the last three are original decals